DEMONSTRATION OF DOPAMINE DA-1 RECEPTOR-SITES IN RAT JUXTAGLOMERULAR CELLS BY LIGHT-MICROSCOPE AUTORADIOGRAPHY

The binding of the selective DA-1 receptor antagonist [3H]-SCH 23390 in sections of rat kidney was studied using combined in vitro biochemical radioreceptor assay and autoradiography. [3H]-SCH 23390 was bound to sections of rat kidney in a manner consistent with the labeling of DA-1 receptors with a dissociation constant value of 4.2 nmol/l and a B(max) value of 180.6 fmol/mg protein. Light microscope autoradiography revealed a dense accumulation of silver grains in juxtaglomerular cells and in proximal convoluted tubule cells. These findings suggest that the stimulation of renin release elicited by dopamine and DA-1 receptor agonists may be mediated by the activation of DA-1 receptors located on juxtaglomerular cells.